This invention relates to a magnetically navigable telescoping catheter and a method of magnetically navigating a telescoping catheter within open body spaces.
Many medical procedures require the ability to accurately navigate medical devices inside the body. In the past, this has been accomplished with mechanically steerable devices. More recently, magnetically navigable medical devices have been developed that can be navigated with an externally applied magnetic field.
However, previously available navigable devices and navigation methods are only marginally acceptable for some procedures where high precision is required. For example, in certain cardiac procedures such as mapping (recording electrical impulses on the surface of the heart); pacing (inducing electrical impulses of the surface of the heart); and ablation (applying RF energy to the heart tissue to ablate the tissue to block stray electrical signals that cause arrhythmias) an electrode must be precisely controlled to contact specific points on the heart. One treatment of cardiac arrhythmias relies upon the formation of a continuous linear lesion from a series of contiguous spot lesions. Such a procedure can be extremely tedious and time consuming with previously available devices and navigation methods.
Examples of mechanically controlled catheters for such procedures include Avitall, U.S. Pat. Nos. 5,354,297, 5,327,905, and 5,642,736; Webster, U.S. Pat. No. Re 34,502; West et al., U.S. Pat. No. 5,318,525; and Webster, Jr., U.S. Pat. No. 5,626,136. These mechanically actuable catheters typically have a limited number of directions of movement. Moreover to navigate the distal end of the catheter to a particular point, the catheter had to be rotated, but rotation of the proximal end of the catheter did not always directly translate to rotation at the distal end, particularly where the path of the catheter was convoluted. Moreover, twists and turns in the catheter would impair or eliminate the ability to control the distal end of the catheter.
Magnets have also been used in such devices. Scheinman, U.S. Pat. No. 5,429,131 and Grayzel, U.S. Pat. No. 4,809,731. However, not for navigation.
The present invention relates to a magnetically navigable telescoping catheter, and to a method of navigating such catheter in the body. Generally, the magnetically navigable telescoping catheter of the present invention comprises a sleeve having a proximal end and a distal end. An extension member having a proximal end and a distal end is slidably mounted in the sleeve so that the distal end portion of the extension member telescopes from the distal end of the sleeve. The distal end portion of the extension member is relatively more flexible than the distal end of the sleeve. At least one magnet is positioned on the distal end portion of the extension member to allow the distal end of the extension member to be oriented by the application of an externally applied magnetic field. The position of the distal tip of the catheter can be controlled by the controlled application of a magnetic field to orient the distal end of the extension member, and telescoping the extension member into and out of the sleeve. At least one electrode is positioned on the distal end of the extension member.
In accordance with a preferred embodiment of this invention, a sheath is also provided, and the sleeve is slidably mounted in the sheath so that the distal end of the sleeve can telescope relative to the distal end of the sheath. In navigating the catheter of the preferred embodiment, in addition to the direction control provided by the controlled application of a magnetic field and the telescoping of the extension member relative to the sleeve, the user can also telescope the sleeve relative to the sheath to control the position of the distal end of the extension member. This gives the user a first adjustable length whose direction is controlled by the direction of the magnetic field, and a second adjustable length substantially unaffected by the direction of the magnetic field.
The catheter can be provided with one or more electrodes for cardiac mapping, pacing, or ablation. Alternatively, the catheter can be used in some other procedure such as the delivery of therapeutic agents.
According to the method of this invention, the distal end of the extension member is navigated to the site in the body. Once in the desired location, a magnetic field is applied to orient the distal end portion of the extension member, and the distal end is navigated to a precise location by the relative telescoping of the extension member relative to the sleeve, and in the preferred embodiment also by the relative telescoping of the sleeve relative to the sheath.
With this method, an electrode on the end of the distal end of the extension member can be navigated to contact specific parts of the body, for example the chambers of the heart, to bring an electrode into contact with the tissue for mapping, pacing, or ablation.
The telescoping motion and magnetic guidability of the electrode catheter of the present invention allows superior control of the distal end of the catheter, without regard to the path of the catheter. The improved navigation is both faster, reducing procedure times, and more accurate, allowing the procedures to be successfully completed. However the catheter is of relatively simple and reliable construction. These and other features and advantages will be in part apparent and in part pointed out hereinafter.